Holidaymakers using the Stansted Express will face disruption today as train staff embark on a 48-hour strike.
The train between Liverpool Street and Stansted is running an hourly service today instead of the usual service every 15 minutes.
Trains will run with 12 carriages, rather than the usual four to eight, to help compensate for the disruption, and extra coach services are available between the airport and London.
A spokesman for Stansted Airport said staff would be on hand to advise holidaymakers.
The 48-hour strike by members of the Rail Maritime and Transport union and ASLEF is over pay and conditions. Three more strikes are planned for Thursdays and Fridays in August.